Dinamika Pelepasan Nitrogen Empat Jenis Pupuk Urea pada Kondisi Tanah Tergenang

Abstract

Nitrogen (N) merupakan salah satu unsur hara esensial bagi tanaman. Salah satu penyebab rendahnya ketersediaan N adalah pencucian. Pupuk urea merupakan sumber hara N yang paling banyak digunakan di Indonesia, termasuk pada lahan sawah. Urea merupakan pupuk N yang larut air sehingga penggunaan urea di sawah perlu dikaji dalam hubungannya dengan pelepasan pupuk. Di dalam penelitian ini digunakan urea dengan formulasi berbeda yaitu urea kujang dan pusri yang merupakan urea konvensional dan urea prill dan granul yang merupakan urea modifikasi yang mengandung formaldehida masing-masing 0,10 dan 0,50 %. Metode yang digunakan adalah inkubasi dan pencucian. Inkubasi dilakukan selama 7, 14, 28, 45, 60, dan 90 hari dan dilakukan pencucian pada setiap akhir masa inkubasi. Hasil pencucian ditetapkan kandungan amonium dan nitrat. Hasil penelitian menunjukkan bahwa pelepasan N dalam bentuk amonium dan nitrat antar perlakuan pupuk urea tidak berbeda nyata. Hasil total N tercuci menunjukkan nilai paling tinggi diperoleh oleh urea granul sebesar 78,0 mg tabung-1, kemudian disusul oleh urea prill 75,2 mg tabung-1, urea kujang sebesar 71,5 mg tabung-1, dan urea pusri sebesar 68,4 mg tabung-1. Berdasarkan hasil persamaan first order kinetic, diperoleh nilai pelepasan maksimum dan konstanta kecepatan. Nilai pelepasan maksimum tertinggi dimiliki oleh urea granul sebesar 94,6 mg tabung-1, kemudian urea prill sebesar 88,3 mg tabung-1, urea pusri sebesar 82,3 mg tabung-1, dan urea kujang sebesar 79,2 mg tabung-1. Sementara untuk nilai konstanta kecepatan, konstanta kecepatan tertinggi diperoleh pada urea kujang sebesar 0,0349 hari-1, kemudian dilanjutkan oleh urea prill dan pusri sebesar 0,0256 hari-1, dan urea granul sebesar 0,0253 hari-1. Hasil penelitian menunjukkan bahwa urea yang diperlakukan dengan formaldehida terutama dalam bentuk granul cenderung memiliki kemampuan untuk memperlambat proses pelepasan N yang ditunjukkan dengan nilai konstanta kecepatan yang paling rendah.

Nitrogen (N) is one of the essential nutrients for plants. One of the causes of the low availability of N is leaching. Urea fertilizer is the most widely used source of N in Indonesia, including in paddy fields. Urea is a water-soluble N fertilizer, so the use of urea in paddy fields needs to be studied in relation to the release of fertilizer. In this study, urea with different formulations was used those were urea kujang and pusri as conventional urea, while urea prill and granule as modified urea containing 0,10 and 0,50 % formaldehyde, respectively. The method in this study was the incubation and washing method. Incubation was carried out for 7, 14, 28, 45, 60, and 90 days and washing was conducted at the end of each incubation period. The results of washing were determined for the content of ammonium and nitrate. The results showed that the release of N in the form of ammonium and nitrate among urea fertilizer types were not significantly different. The results of total leached N showed that the highest value was obtained by granul urea at 78,0 mg tube-1, then followed by prill urea at 75,2 mg tube-1, kujang urea at 71,5 mg tube-1, and pusri urea at 68,4 mg tube-1. Based on the results of the first-order kinetic equation, it was revealed the maximum release and constant rate. The highest value of maximum release was obtained by granul urea at 94,6 mg tube-1, then followed by prill urea at 88,3 mg tube-1, pusri urea at 82,3 mg tube-1, and kujang urea at 79,2 was mg tube-1. As for the rate constant the highest value of rate constant was obtained by urea kujang at 0,0349 day-1, followed by prill urea and pusri urea at 0,0256 day-1, and granule urea at 0,0253 day-1. The result showed that urea treated with formaldehyde especially in the form of granul tended to slow down the release of N indicated by the lowest value of the rate constant.